Allison S. is a 3,600 bhp class twin-screw tugboat. The vessel is 105 feet (32 m) long, with a breadth of 30.5 feet (9 m) and a depth of 12.5 feet (4 m). Allison S. was constructed by Main Iron Works, Inc. of Houma, La. in nine months and carries an ABS International Loadline. TheAllison S. will be positioned on the Mississippi River near St. Rose, La. to provide ship assistance to the large tankers and grain ships which call in the area. The tugboat will also be available for emergency towage and salvage assignments in the U.S. Gulf area.

Main propulsion is provided by two Detroit Diesel 16V-149TIs driving two Twin Disc MG 540 reduction gears with 7:1 ratio, which in turn drive two four-blade stainless steel propellers, set in stainless steel Kort nozzles.

Electrical power is provided by two Delco 60 kW generators driven by two Detroit Diesel 4- 71s.